package net.oschina.app.widget;

import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.widget.Scroller;

/**
 * 左右滑动切换屏幕控件
 *
 * @author Yao.GUET date: 2011-05-04
 * @modify liux (http://my.oschina.net/liux)
 */
public class ScrollLayout extends ViewGroup
{
    private static final String TAG = "ScrollLayout";
    private Scroller mScroller;
    private VelocityTracker mVelocityTracker;
    private int mCurScreen;
    private int mDefaultScreen = 0;
    private static final int TOUCH_STATE_REST = 0;
    private static final int TOUCH_STATE_SCROLLING = 1;
    private static final int SNAP_VELOCITY = 600;
    private int mTouchState = TOUCH_STATE_REST;
    private int mTouchSlop;
    private float mLastMotionX;
    private float mLastMotionY;
    private OnViewChangeListener mOnViewChangeListener;

    /**
     * 设置是否可左右滑动
     *
     * @author liux
     */
    private boolean isScroll = true;

    public void setIsScroll(boolean b)
    {
        this.isScroll = b;
    }

    public ScrollLayout(Context context, AttributeSet attrs)
    {
        this(context, attrs, 0);
    }

    public ScrollLayout(Context context, AttributeSet attrs, int defStyle)
    {
        super(context, attrs, defStyle);
        mScroller = new Scroller(context);
        mCurScreen = mDefaultScreen;
        mTouchSlop = ViewConfiguration.get(getContext()).getScaledTouchSlop();
    }

    @Override
    protected void onLayout(boolean changed, int l, int t, int r, int b)
    {
        int childLeft = 0;
        final int childCount = getChildCount();
        for (int i = 0; i < childCount; i++)
        {
            final View childView = getChildAt(i);
            if (childView.getVisibility() != View.GONE)
            {
                final int childWidth = childView.getMeasuredWidth();
                childView.layout(childLeft, 0, childLeft + childWidth,
                        childView.getMeasuredHeight());
                childLeft += childWidth;
            }
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec)
    {
        //Log.e(TAG, "onMeasure");
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        final int width = MeasureSpec.getSize(widthMeasureSpec);
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        if (widthMode != MeasureSpec.EXACTLY)
        {
            throw new IllegalStateException(
                    "ScrollLayout only canmCurScreen run at EXACTLY mode!");
        }
        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        if (heightMode != MeasureSpec.EXACTLY)
        {
            throw new IllegalStateException(
                    "ScrollLayout only can run at EXACTLY mode!");
        }

        // The children are given the same width and height as the scrollLayout
        final int count = getChildCount();
        for (int i = 0; i < count; i++)
        {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }
        // Log.e(TAG, "moving to screen "+mCurScreen);
        scrollTo(mCurScreen * width, 0);
    }

    /**
     * According to the position of current layout scroll to the destination
     * page.
     */
    public void snapToDestination()
    {
        final int screenWidth = getWidth();
        final int destScreen = (getScrollX() + screenWidth / 2) / screenWidth;
        snapToScreen(destScreen);
    }

    public void snapToScreen(int whichScreen)
    {
        //是否可滑动
        if (!isScroll)
        {
            this.setToScreen(whichScreen);
            return;
        }

        scrollToScreen(whichScreen);
    }

    public void scrollToScreen(int whichScreen)
    {
        // get the valid layout page
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        if (getScrollX() != (whichScreen * getWidth()))
        {
            final int delta = whichScreen * getWidth() - getScrollX();
            mScroller.startScroll(getScrollX(), 0, delta, 0,
                    Math.abs(delta) * 1);//持续滚动时间 以毫秒为单位
            mCurScreen = whichScreen;
            invalidate(); // Redraw the layout

            if (mOnViewChangeListener != null)
            {
                mOnViewChangeListener.OnViewChange(mCurScreen);
            }
        }
    }

    public void setToScreen(int whichScreen)
    {
        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        mCurScreen = whichScreen;
        scrollTo(whichScreen * getWidth(), 0);

        if (mOnViewChangeListener != null)
        {
            mOnViewChangeListener.OnViewChange(mCurScreen);
        }
    }

    public int getCurScreen()
    {
        return mCurScreen;
    }

    @Override
    public void computeScroll()
    {
        if (mScroller.computeScrollOffset())
        {
            scrollTo(mScroller.getCurrX(), mScroller.getCurrY());
            postInvalidate();
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent event)
    {
        //是否可滑动
        if (!isScroll)
        {
            return false;
        }

        if (mVelocityTracker == null)
        {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(event);
        final int action = event.getAction();
        final float x = event.getX();
        final float y = event.getY();
        switch (action)
        {
            case MotionEvent.ACTION_DOWN:
                //Log.e(TAG, "event down!");
                if (!mScroller.isFinished())
                {
                    mScroller.abortAnimation();
                }
                mLastMotionX = x;

                //---------------New Code----------------------
                mLastMotionY = y;
                //---------------------------------------------

                break;
            case MotionEvent.ACTION_MOVE:
                int deltaX = (int) (mLastMotionX - x);

                //---------------New Code----------------------
                int deltaY = (int) (mLastMotionY - y);
                if (Math.abs(deltaX) < 200 && Math.abs(deltaY) > 10)
                    break;
                mLastMotionY = y;
                //-------------------------------------

                mLastMotionX = x;
                scrollBy(deltaX, 0);
                break;
            case MotionEvent.ACTION_UP:
                //Log.e(TAG, "event : up");
                // if (mTouchState == TOUCH_STATE_SCROLLING) {
                final VelocityTracker velocityTracker = mVelocityTracker;
                velocityTracker.computeCurrentVelocity(1000);
                int velocityX = (int) velocityTracker.getXVelocity();
                //Log.e(TAG, "velocityX:" + velocityX);
                if (velocityX > SNAP_VELOCITY && mCurScreen > 0)
                {
                    // Fling enough to move left
                    //Log.e(TAG, "snap left");
                    snapToScreen(mCurScreen - 1);
                }
                else if (velocityX < -SNAP_VELOCITY
                        && mCurScreen < getChildCount() - 1)
                {
                    // Fling enough to move right
                    //Log.e(TAG, "snap right");
                    snapToScreen(mCurScreen + 1);
                }
                else
                {
                    snapToDestination();
                }
                if (mVelocityTracker != null)
                {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
                // }
                mTouchState = TOUCH_STATE_REST;
                break;
            case MotionEvent.ACTION_CANCEL:
                mTouchState = TOUCH_STATE_REST;
                break;
        }
        return true;
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev)
    {
        if (!isScroll)
        {
            return super.onTouchEvent(ev);
        }
        //Log.e(TAG, "onInterceptTouchEvent-slop:" + mTouchSlop);
        final int action = ev.getAction();
        if ((action == MotionEvent.ACTION_MOVE)
                && (mTouchState != TOUCH_STATE_REST))
        {
            return true;
        }
        final float x = ev.getX();
        final float y = ev.getY();
        switch (action)
        {
            case MotionEvent.ACTION_MOVE:
                final int xDiff = (int) Math.abs(mLastMotionX - x);
                if (xDiff > mTouchSlop)
                {
                    mTouchState = TOUCH_STATE_SCROLLING;
                }
                break;
            case MotionEvent.ACTION_DOWN:
                mLastMotionX = x;
                mLastMotionY = y;
                mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST
                        : TOUCH_STATE_SCROLLING;
                break;
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                mTouchState = TOUCH_STATE_REST;
                break;
        }
        return mTouchState != TOUCH_STATE_REST;
    }

    /**
     * 设置屏幕切换监听器
     *
     * @param listener
     */
    public void SetOnViewChangeListener(OnViewChangeListener listener)
    {
        mOnViewChangeListener = listener;
    }

    /**
     * 屏幕切换监听器
     *
     * @author liux
     */
    public interface OnViewChangeListener
    {
        public void OnViewChange(int view);
    }
}